Railroads often use wayside signal cantilevers to mount light signals (e.g., red/yellow/green signals) in locations where there are multiple parallel tracks and the signals cannot be mounted on masts due to lateral clearance restrictions between the track centers. The position of each signal with respect to the associated track is safety critical to ensure locomotive engineers always know which signals apply to their tracks. Cantilevers allow the signals to be mounted over the tracks, therefore eliminating lateral clearance issues on the sides of each track while allowing the signals to be correlated with each track to avoid confusion. In some situations, for example when the number of parallel tracks or the distance between tracks is too great to allow for a stable cantilever structure, a bridge structure may be used with vertical supports on both sides of the tracks.
FIG. 1A is a railway wayside signal cantilever structure 100. The structure 100 includes a support 110 and cantilever 120 extending over two tracks 10, 11. Two sets of light signals 150, 151 are mounted on the cantilever 120, one for each track 10, 11. The structure 100 may include a ladder 115 and walkway 125 to allow maintenance access to the light signals 150, 151. Light signals 150, 151 may be present on multiple levels (two are shown in FIG. 1A), each with a walkway 125. In this example, light signals 150, 151 are positioned 3-4 feet from the centers of their associated tracks 10, 11. A train operator can thus easily tell which light signal 150, 151 corresponds to which track 10, 11.
FIG. 1B is a railway wayside signal bridge structure 1000. The structure 1000 includes a pair of supports 1010, 1011 and bridge 1020 extending over four tracks 12, 13, 14, 15. Four sets of light signals 1050, 1051, 1052, 1053 are mounted on the bridge 1020, one for each track 12, 13, 14, 15. The structure 1000 may include a ladder 1015 and walkway 1025 to allow maintenance access to the light signals 1050, 1051, 1052, 1053. Light signals 1050, 1051, 1052, 1053 may be present on multiple levels (two are shown in FIG. 1B), each with a walkway 1025. In this example, light signals 1050, 1051, 1052, 1053 are positioned 3-4 feet from the centers of their associated tracks 12, 13, 14, 15. A train operator can thus easily tell which light signal 1050, 1051, 1052, 1053 corresponds to which track 12, 13, 14, 15.
The distance between adjacent tracks may vary among locations due to environmental variables such as landscaping and space restrictions. As a result, the positions of cantilever or bridge mounted overhead signals may vary among locations, and cantilevers and bridges are designed and configured in the factory to work in the specific location in which they are to be installed.